Mechanism for controlling movement.



F. A. H. 'HARLE.

MECHANISM FOR CONTROLLING MOVEMENT.

APPLICATION FILED JULY 21,1914.

1,268,712. Patented June 4,1918.

8 SHEETS-SHEET 1- F. A. H. HARLE. MECHANISM FOR CONTROLLING MOVEMENT. APPLICATION FILED JULY 2!, I914.

1,268,? 12. Patented June 4,1918.

8 SHEETSSHEET2.

Q05, fuwugz mii;

F. A. H. HARLE'.

MECHANISM FOR CONTROLLING MOVEMENT APPLICATION FILED JULY 2|, 1914.

1 ,7 1 2 Patented J une 4, 1 918.

8 SHEETSSHEET 3.

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' F. A. H. HARLE.

MECHANISM FOR CONTROLEING MOVEMENT. APPLICATION FILED M121. 1914.

1,268,712. v Patented June 4,1918.

8 SHEETS-SHEET 4.

r. A. a. "ABLE. MECHANISM FOR CONTROLLING MOVEMENT.

APPLICATION FILED JULY 2!.1914.

1,268,? 1 2. Patented June 4, 1918.

F. A. H.- HARL E. nEcuAui'Sn ron con'moum'n MOVEMENT.

APPLICATION FILED JULY 21.1914.

1,268,7 1 2. Patentod June 4, 191&

B SHEETS-SHUT I F. A. H. HARLE.

I MECHANISM FOR CONTROLLING MOVEMENT. APPLICATION FILED'JULY'ZI. 1914.

Patented June 4, 1918.

8 SHEETS-SHEET 7- I F. A., H. HARLE. MECHANISM FOR CONTROL'LING MOVEMENT. APPLICATION FILED JULY 21. I914.

1,268,712. Patented June 4, 1918.

V a SHEETS-SHEET a.

. To all whom it onc'em:

uevsrn HENRI 01? fans, FRANCE.

macnmsm ron ,CONTBOLLDIG movrinnn'n v Applicatioh med'J'1i1y 21, 1914. sem in. 852,181.

" Be it known that], FmimiRIo AUGUSTE' HENRI. HARLIQ of 26 Avenige de Sufiren, 1 Paris, France, engineer, have invented new 1 and useful Improvement in Mechanism for are fully set forth in the following specification. I

' In electric control apparatus'it has already been proposed to control a motoractuating the controlled member by the balance cura rentv of an electric arrangement identical with or similar to a Wheatstone bridge. When. the balance is upset to a given extent at the control .stationfth current thlls generated in the. balance wire sets the motor running until it reestablishes equilibrium by acting upon the relation ofthe resistances ofthe other arm of the bridge.

A known arrangement of'control is illus-v trated diagrammatically in Figure 1.

- similarly arranged and provide .with resistances "d and d At the control station a handle a has on it' a contact I) which moves in a circular path to vary the resistance of thetwo arms 0 c of a Wheatstone bridge provided if desired bridge are The two other arms 6 e ofthg f d i desire with resistances 7 f at the controlled sta tion whose index or controlled member 9 carrying contact g is moved by a motor 71..

- The motor h 1s controlled ,by a galvanometer relay 1; interposed in the bridge balance wire j connected to the contact .bars 8 and 1'; this relay has contacts 70 and Zwhich control through relays m n the movement of the motor in one or other-direction.

Under these conditions when the handle a at the control station is movedthe motor h. starts running and brings thewindek at the controlled station intothe correspon in position. so soon as such position is reached the motor h stops.

A control of this type has the defect that when the handle a is movedso that its contact 2) comes to either of the extreme ends 0 or. 0 of the resistances 0 c and'moves onacross to the. other extreme end the index 9 at the controlled station does not follow this movement instead of passing throu h the corresponding-points p 12 it turns int reverse direction and regains the position of balance at the other side this is due to w speci-ilcafionot Letters Patent.

1 nometer relay.

' index g.

Patented J une 4, 1918.

movement of *thegalvanometer relay 2' and employed the action of each being'eliminated n this- "1nvent1on"s eve ral" ,Wheatstone briges are Controlling Movement, which improvements 'at' 'th'e points at which such reversal could take place.

.The accompanying drawings illustrate di agrammatically several ways of carrying out 4 the invention. o v

' Figs. 2,. 3 and 4- difier from each other in the number or alrran emen tof the bridges.

Fig. 5, shows a mo ifi cation of Fig.6 shows a modification as regards the arms of the bridges."

Figs. 7 and 8 show a modification as re-' gards the method of putting the'bridges out of action at the desired moment.

I Fig. 2 shows two bridges connected in parallel. One bridge comprises the same elements as shown in Fig.1, that isto say, at

the control station there are resistances c,c

connected with the mains, if desired through resistances d, d the resistancesc, 0 being varied by movement of -the contact 6, carried onhandle a, over the contact bar .9, said contact bridging the resistances and bar as the galva shown. Atthe controlled station there are resistances e, 6 connected with the mains, if desired through res stances f; f the resistances 6, 6 being varied by movement of 'the i dex g. carrying contact 9 over the contact bar 1', said contact being designedv t0 bridge the resistances and bar as shown.

Balance wire 7' is connected with the contact bars rand s,.-and interposed therein is'the 1 galvanometer relay 1? for controlling the operation of the motor h WhlCh moves'the In parallel with control station the resistances c' 0'. con: nected to the mains, if through the resistances d al the resistances a, 0 being varied by movement of the contact 6, which may beconveniently'carried on the opposite this contact bridgin resistances 6', 6' being varied by contact which may be convemently carried on t e opposite end of index 9', along theeontact the above bridge circuit I is a second bridge circuit comprising at the bar r, said contacts bridging the resistances 6, 6' and the bar 7". The contact bars a and 1" are connected by the balance wire y" in which is interposed the galvanometer relay i. The motor h is controlled through the relays m and 'n by the relays z' and i, the latter relays being constructed to close contacts is or Z and k or Z respectively.

To cut out the wire when the contact 9' is near points p and the contact bar 1' does not extend through a complete circle as does the contact bar 8, but only through a little more than a semicircle, as clearly shown on the drawing; Similarly, to cut out the balance wire j when the contact 9 is near the points p or 2 the contact bar 71' is similarly limited to a little more than a semicircle, as shown.

In this arrangement no reversal will take place .by movement of the handle a from point 0 to 'point 0 or vice versa, provided the handle a be moved approximately at the s eed with which the motor h drives the inex g or otherwise expressed, so long as the relative angularity of the handle a to the index 9 does not exceed the angle between the radii connected respectively to the end of the, contact bars 7" and 1" and the points 10 or p,, designated on the drawing as a. Thus, assuming the parts to be in the position shown in full lines in Fig. 2, contact g is not in engagement with contact bar 7" and balance wire j is therefore cut out. As-

suming that the handle a is moved in a clockwise direction at approximately the I speed at which the motor It can drive the index 9, as the handle a is moved toward the point 0 index 9 will follow in the same direction and contact 9' will come into engagement with contact bar 1*. By the time contact b has engaged point 0 contact 9 is ready to pass out of engagement with contact bar 1'. Consequently, as the contact b is moved from point 0 to point 0, balance wire 7' is cut out and the motor h is under the control solely of the balance wire j 'three galvanometer 'on relays i z" i" acting which, as will be apparent, will maintain the motor running in the same direction. Obviously the same result will occur if the con- .tact b be moved from the point 0 to point 0 in an anti-clockwise direction.

It is furthermore to be noted that handle a may be moved, however quickly, within certain limits of its circle of movement and be followed by the index 9 in the same direction. Thus the handle a may be moved rapidly from a position wherein contact 9' is out of engagement with bar r, a shown in full-line position in Fig. 2, in a clockwise Y or anti-clockwise direction to any portion .of the greater are between t, and t, and be followed by the index 9 in the same direction because, at starting, the balance wire j 1SCllt out (since contact g is not in engagement with bar 1" as shown in the dotted-line position indicated at 1 in this figure, the handle a may be moved rapidly in a clockwise or anti clockwise direction to any portion of the greater are between 0 and 0, and be followed by the index 9 in the same direction because, at starting, the balance wire j is cut out (since the contact 9 is not in engagement with bar 1") and when the balance wire 7' is cut in, it will not within these limits undergo a change in the direction of the current flowing therethrough. Similarly, if the index 9 is in any of the positions indicated in dotted lines at 2, handle a may be moved rapidly in either direction to any portion of the are 0 -25,, and if the index 9 is in any of the positions indicated in dotted lines at 3, handle a may be moved rapidly to any point in the arc owt, and be followed by the index g in the same direction, because, while the motor may be under the control of both balance wire j and j within these limits, neither will undergo a change in the direction of current flowing therethrough.

Therefore, by the constructionof Fig.- 2, the handle a may be moved through one or more revolutions and be followed by the index 9 in the same direction of rotation through the same number of revolutions if the angularity between the two he kept within the angle a as explained;

In place of two bridges, as in Fig. 2, three may be employed as illustrated in Fig. 3. Similar parts are indicated by similar letters, the characters designating the second and third bridge elements being differentiated from those designating the first bridge elements by one and two primes respectively.

As shown, this arrangement comprises upon the motor h through relays m' and a.

Contact bars 1" -1 1'" are also provided which do not make a complete circle' As illustrated the angle a is larger than in the arrangement of Fig. 2 nevertheless one bridge at least is always in circuit.

A reater number of bridges may be provide on the same principle.

It is not necessary that a bridge should extend through the entire circle as in Figs. 1, 2 and 3; an arrangement in which it extends through a half circle only is illustrated in Fig. 4. l 4 y In this figure there are two bridges 0 c and a 0',; the elements and their working are the same as in Fig. 2 except that the handle carries two pairs of contacts I) b and .structions oi'rFigs. 2 or 4.

'3 6' 90 apart one or the other of which come alternately into contact with the bridges. At thecontrolled station the bridges may be arranged as in Figs. 2, 3 or 4' or as in Fig. 6 hereinafter described.-

Referring-to Fig. 3,iit has been supposed that there are galvanometer relays i z" i, one on each of the balance wires 7' j .j".

While a bridge is out of action by reason of the corresponding contact on the index not engaging oneof the contact bars r r r";

its galvanometer relay comes back to zero.

As this relay possesses a certain inertia this movement takes-place with a certain lag. This may be avoided by replacing the galyanometer relays by a single relay comprismg as many windings as there are bridges,

;two in Figs. 2 and 4 and three in Fig. 3.

Fig. 5 illustrates gthe employment of a single galvanometer relay 71 having two windings which may be applied to the con.

The Wheatstone bridges. as previously illustrated are distinct one from the other.

Consequently for example as in Fig. 2, when the current is broken in the'balance wire by the disengagement of the contact 9 from contact bar 1' no variation occurs in the balance current of the wire 7" and thereforeno disturbance in the working of the relay '5' or in the working of the motor. 5

If as a modification of this invention the bridges are not distinct but utilize, for example as in Fig. 6, the same resistance 0 0 'I as a bridge arm, the relays i and i must have a great electrical resistance in order that the balance current in the wire 7' ma be small enough for its variations to be without substantial influence upon the yalue of the current in j and reciprocally.

Referring to Fig. 6, the control station hastworesistances 0, 0 connected to th'e'mains', if desired through resistances (1,. 1,. 'The handle a is provided with a contact '6 to connect the resistances to acontact bar 8 Y and with a pair of. separated butelectrically but electrically-connected contacts g adapted to connect the resistances to a second contact bar 1", the insulation between said con- ,"tacts g insulating the same from the" con.-

tact bar r. The contact bars r and s are con- 1 nected by the balance wire j in which is the galvanometer relay z, and the contact bars and 8', are connected by the balance wire j f is the galvanometer relay 2". The

relays i and i respectively control contacts 70, Z and k, L in circuit with the relays m and 'n which control the operation of the motor 72., as, in the modification of Fig. 2. The contact bars 1', r at the controlled station extend throu h less than a complete circle as in the modi cation ofFig. 2, while the corresponding bars 8', 8 at the control station extend through a complete circle. It is evident that the equivalent result could be obtained by making the contact bars 1', r a complete circle andthe contact bars 8, 8 less than a complete circle.

Assuming the parts to be in the position shown in full-lines in Fig.6, the'balance wire j is cut out as the contacts 9'- are'out of electrical connection with the contact bar r". A movement of the handle a'will be followed by a correspondingmovement of the index 9 precisely as in the modification of Fig. 2,

the elements operating as described in .con-

nection with that construction. When the contacts g electrically connect the resistances with the contact bar r, there will be corresponding reductions in the two currents flowing through the resistances c and e to and from the contacts '17 and g-respectively, as part of the current will flow through contacts b and bar 8'. and through contacts 9 and bar r and through the balance 'wire 9''.

The index 9 is now'under the control of the two bridge circuits which operate in precisely the same way as in the modification of Fig. 2. When the contact gpasses outof engagement with contact bar 1', the balance wire j is cut out, but the two contacts 6 00-.

operating with resistances 0, c and contact bar 8 and the two contacts 9 'coiiperating with resistances e, e, and contact bar 1", operate to control the galvanometer relay 2', in precisely the same way as when the contacts 6 and g in the modification of Fig. 2 are out of contact with contact bars 8 and r respectively. Other arrangements may also be employed for putting a bridge out of action. Fig. 7 shows one example and comprises two relays u u, in series, one at the control station the other at the controlled station.

When excited they cut out the balance Wire 7' and connect the galvanometer relay i to the wire j; when they are not excited they cut out the wire 7' and connect the relay 2' to j.

The relays u, u, are controlled by press buttons 0, '0 and w, 'w, in circuit therewith, the buttons '0, '0 bein normally held open to maintain the circuit through the relays open, and the buttons w, "20 being normally held closed to maintain the -circu1t through the relays closed. Said buttons. are positioned in the path of and designed to be operated by the heads of the handle a and index 9.

Assuming the para in the position u and u, operate the contacts to cut balance '10 wire j out of circuit with relay iand to cut the balance wire j into circuit .with said relay. The operation of the relay u will also bridge the contacts at w so as to-maintain a circuit through the relays wand u and the parts in the position to which they have been moved, even though the button. 12 be again opened. Obviously the same could be accomplished by closing the button 'v If the handle a be, then swung through 180 in an anti-clockwise direction, it w ll open the button w in passing the same and break the circuitthrough the relays u and u,. The balance wire y" will now be cut out of circuitwii h relay 2' and the balance wire 9" will be cut into said circuit. This operation of relay u also breaks the electrical connection at w, and the circuit will not be com pleted if the button 11) be again closed. IOb-v viously the same efl'ect could be accomplished by opening the button '10,.

If the handle a and index 9" are in the position shown in this figure and the handle" is moved suddenly clockwise through 180, the motor. h, if controlled solely by balance wire j, would be reversed. Owing tothe closing of the button 2) and the consequent cutting out of balance wire j and cutting in of balance wire 1', no reversal takes place however. Similarly, if the handle a were swung through 180 in an anti-clockwise direction, and the motor 72. were controlled solely by the balance wire j, it would be reversed. Owing to the opening of the button w and the consequent cutting out of balance wire y" and cutting in of balance wire j, however, no reversal takes place.

It will therefore be observed that so long as. handle a is moved at such aspeed as not to make with index 9 an angle greater than 180, there will be no reversal of the motor h and the index 9 will follow the handle a through one or more turns in the same dlI'GC-r tion. Furthermore, the handle a may be moved quickly through an arc of less than 180 and it will be followed by the index 9 rotating in the same direction.

As such control arrangement has no dead. point it is capable of numerous applications other than that of a single control at a distance. For example Fig. 8- indicates its application to increase the precision of a control in'accordanc'e with Fig. 1.

Referring to this figure, which has been somewhat simplified for the sake of clear designed to connect the resistances to the contact bar a. At thecontrolled station index g is provided with separated electrically-connected contacts 9 designed to contract the resistances with the contact bar or The contact bars sand r are connected by the balance wire 7' through the relay i as heretofore described.

At the control station a second contact member a, is mounted concentrically with thehandle a and is driven therefrom through the speed-increasing gearing 31 Contact member an carries a pair of separated electrically-connected contacts 6 to connect the resistances with contact bar 8 and a contact b to connect the resistances with contact bar 8' Similarly at the controlled station a second contact member 91 is mounted concentrically with the index g to be driven therefrom through the speedincreasing gearing y The two sets of speed-increasing gearing 3 3 have the same ration. Contact member 9 carries two separated electrically-connected contacts 91 designed to connect the resistance with contact bar 1' and a contact g designed to connect the resistances with contact bar 'r Contact bars 13 and 8 and r, and 8' are respectively connected by the balance wires j 'which include separate coils of a double winding of the galvanometer relay 2', as described in connection with Fig. 5.

Relays i and 5 respectively control the motor h through the relays m and n, as-

heretofore disclosed. The circuit through the relays m and n, which includes the relay 2', additionally includes a relay .2 which is designed to operate a pair of contact members 2 2' in the balance wires 7' 7",.

-When the handle a and the index 9 are relatively at a small angle the current which passes through the wire j is too small to move the galvanometer relay Therefore, without the aid of the bridges including the balance wires 7' j',, the motor it would not be put into action, and the small error would persist. Owing to the speed mcreasing" gearing between the handle a and the contact member a and between the 1ndex g and the contact member 9 the small angle between the handle a and index 9 is considerably multiplied as between the contact members a, and 9 so that the current passing through the wires j j, is muchlarger than that passing through the wire The galvanometer relay 71 will therefore control the motor 71, and the accuracy of control will be increased. 1

- When the handle a and the index' 9 are at a larger angle,

the balance wire 7' is sufiicient'to actuate the "the current flowing through relay z'. The closing-of the circuit through the relays m and n by the relay i also closes the circuit through the relay 2, whereupon contact members 2 2', are moved' to cut out the balancecircuits through the wires 1' 7",.

This prevents the possibility of a reversal of the motor which might be produced by the bridges including the balance wires 7' j, if, as described in connection with Fig. 2, the

contact members a, and g,' shouldbe at an ployed asangle greater than a.

As but single sets of resistances are em-. in the modification disclosed in Fig. 6, it will be understood that when the motor is under the control of the bridges including balance wires j, the motor is controlled in the same manner as described with respect to said figure. Furthermore,

as in the construction shown in Fig. 1, the

motor 7 will not be reversed when controlled respectively.

versa,

solely by the relay [so long as the contact I) i 'does not pass from one-extreme position 0 to the other extreme position 0 or vice control given contact members a, and 9, by the speed-increasing gearing y and y, between said members and the handle a and index 9 p k It will be apparent that theaccuracy of control may be still further increased by increasing the number of contact members at the two-stations, and'by the selection of proper speed-increasinggearing which will make the contact members move at difierent speed ratios As in 'Fig.- 8, the motor-control circuits ofsuch a construction would include relays to cut\out the balance circuits in succession.

Having now particularly described and ascertained the nature pf our saidinvention and in what manner the same is to be per formed, we declare that what we claim" is:

v 1. In control apparatus,Wheatstone bridge mechanism comprising resistances at a control station, resistances at .a controlled station, a plurality of balance circuits between said sets of resistances, movable contacts in electrical connection with said first-named resistances and said balance circuits for i varying the resistances at the control, station, movable contacts in electrical connection with said lastnam'ed res stances and said balance circuits for varying the resistances at the controlled station, a motor for moving said last-named contacts, and relay mechanism controlled by said balance circuits for controlling'the operation of said motor. 1

2. In control apparatus, Wheatstone bridge mechanism comprising resistances at a mm but will possess greater accuracy 0t because of the multiplied movement trol station, resistances at-a controlled station, a pluralityof balance circuits between said sets of resistances, movable contacts in electrical connection .with said first-named tion, a plurality of contact bars at the control station, resistances at a controlled statrol station, a plurality of contact bars 'at' the controlled station, movable contacts at the-control-station for conrrecting the resistances to the respectivecontact bars at said station, -movable contacts at the controlled station for connecting the resistances to the respective contact. bars at said station, a plurality of balance circuits connecting the contact bars at the two stations, a motor for moving said last-named contacts, and relay mechanism controlled by said balance circuits for controlling the'operation of said motor. 7

' 4. In control apparatuaWheatstone bridge mechanism comprising resistances at a con-' trol station, resistances at a controlled stat1on, a plurall of contact bars at thecontrol station, a plurality of contact bars at the controlled station, movable contacts at the control station for. connecting the resistances to the respective contact bars at;

saidstation, movable contacts at the controlled station for connecting the resistances to the respective contact bars at said station,

a plurality of balance circuits connecting the contact bars at the two stations, means' whereby each of said balance circuits is predeterminately cut out by the movement of one of said sets of movable contacts, a motor for moving said last-named contacts, and relay mechanism' controlled, by said balance circuits for controlling the opera'-' tion of said motor.

5. In control apparatus- Vyheatstone bridge mechanism comprising resistances at'a control station, resistances at la controlled station, a plurality of contact bars at the control station, aplu'rality of contact bars at the controlled statiou movable contacts at the control station forjconnecting the resistances to the respective "contact bars at i said station, movable. contacts at "the; controlled stationg for connecting the resistances to the respective. contact bars at said statlonya plurallty of balance circuits connect moving said last-named contacts,

ing the contact bars at the two stations,.each

of said contact bars of one set being broken whereby the corresponding movable contacts predeterminately cut out each of said balance circuits, a motor for moving said lastnamed contacts, and relay mechanism controlled by said balance circuits for controlling the operation of said motor.

6. In control apparatus, Wheatstone bridge mechanism comprising resistances at a control station, resistances at a controlled station, a plurality of balance circuits between said sets of resistances, movable circumferentially-spaced contacts in electrical connection with said first-named resistances and said balance circuits for varying the resistances at the control station, movable cir cumferentially-spaced contacts in electrical connection with said last-named resistances and said balance circuits for varying the resistances at the controlled station, a motor for moving said last-named contacts, and relay mechanism controlled by said balance circuits for controlling the operation of said motor.

'7. In control apparatus, Wheatstone bridge mechanism comprising resistances at a control station, resistances at a controlled station, a plurality of balance circuits between said sets of resistances, movable -cireumferentially-spaced contacts in electrical connection with said first-named resistances and said balance circuits'for varying the resistances at the control station, movable circumferentially-spaced .contacts in electrical connection with said last-named resistances and said balance circuits for varying the resistances at the controlled station, means for predeterminately cutting out each of said balance circuits, a motor for moving said last-named contacts, and relay mechanism controlled by said balance circuits for controlling the operation of said motor. 4

.8. In control apparatus, Wheatstone bridge mechanism comprising resistances at a controlstation, resistances at a controlled station, a plurality of contact bars at the control station, .a plurality of contact bars at the controlled station, movable circumferentially-spaced contacts at the control station'for connecting the resistances to the rerspective contact bars at said station, movable circumferentially-spaced contacts at the controlled station for connecting the resisances to the respective bars at said station, a plurality of balance circuits connecting the contact bars at the two stations, a motor for mechanism controlled by said balance circuits for, controlling the operation of said motor.

I 9. In Wheatstone control apparatus,

' bridge mechanism comprising resistances at acontrol stat1on', 'res1stances at a controlled and relay station, a plurality of contact bars at the control station,-a plurality of contact bars at the controlled station, movable circumferentiallyspaced contacts at the control sta tion for connecting the resistances to the respective contact bars at said station, movable circumferentially-spaced contacts at the controlled station for connecting the resistances to the respective bars at said station, a plurality of balance circuits connecting thc'contact bars at the two stations, means whereby each of said balance circuits is predcterminately cut out by the movement of one of said sets of movable contacts, a moable circumferentially-spaced contacts at the controlled station for connecting the resistances to the respective bars at said station, a plurality of balance circuits connecting the contact bars at the two stations, each of said contact bars of one set being broken whereby the corresponding movable contacts predeterminately cut out each of said balance circuits, a motor for moving said last-namedcontacts, and relay mechanism controlled by said balance circuits for controlling the operation of said motor.

' 11. In control apparatus, Wheatstone bridge mechanism comprising resistances at a control station, resistances at a'controlled station, a rotatable handle at the control station, concentric contact bars at the control station coaxial with said handle, a rotatable indexat the controlled station, concentric contact bars at the controlled station c0- axial with said index, movable circumferentially-spaced contacts carried by said haddle and index respectively for connecting" the respective resistances to the respective bars, a plurality of balance circuits connecting the contact bars at the two stations, a motor for moving said index, and relay mechanism controlled by said balance circuits for controlling the operation of said motor.

12. In control apparatus, Wheatstone bridge mechanism comprising resistances at a control station, resistances at a controlled station, a rotatable handle at the control station, concentric contact bars at the control station coaxial with said handle, a rotatable index at the controlled station, concentric contact bars at the controlled station coaxial with said index, movable. circumferentially-spaced contacts carried by said handle and index respectively for connecting the respective resistances to the respective bars, a plurality of-balance circuits connecting the contactbars at the two stations, means for predeterminately cutting out each of said balance circuits, a motor for moving said index, and relay mechanism controlled by said balance circuits for controlling the opindex respectively for connecting the -respective resistances to the respective-bars, a plurality of balance circuits connecting 'the contact bars at the two stations, means whereby each of said balance circuits is predeterminately cut out by the movement of one of said sets ofmovable contacts, a motor for moving said index, and relay mechanism controlled by-said balance circuits for controllingthe operation of said motor. v

14. In control apparatus, Wheatstone bridge mechanism comprising resistances at' a control station, resistances at a controlled station, a rotatable handle at the control station, concentric contact bars at the control station coaxial with said handle,.a rotatable index at the controlled station, concentric contact bars at the controlled stationeoaxial with said index, movable circumferentiallyspaced contacts carried by. said-handle and.

inde'xrespectively for connecting the respective resistances to the respective bars, a plu- 'rality of balance circuits connecting the contact bars at the two stations, each of said fcontact bars of one setbeing broken whereby the corresponding movable contacts predeterminately cut out each of said balance circuits, a motor for moving said index, and

relay mechanism controlled by said balance circuits for controlling the operation of said motor.

15, In control apparatus, a plurality of Wheatstone bridge circuitsin parallel, means for varying the resistances of said circuits, said, circuits and resistance-varying meansbeing so related that the dead-points of the respective circuits areznbn-coincident, and

relay mechanism controlled by the'balance circuits of said bridge circuits. 16. In control apparatus, a plurality of Wheatstone bridge circuits, means for vary- ,,1n'g the resistances of said circuits, said ance circuit connecting saidsets o circuits and resistance-varying means being so related that the dead-points of the respective circuits are nonacoincident, means for cutting out one of said circuits while another ofsa d circuits isclosed, and relay mechanism controlled by the balance circuits of said bridge circuits.

17. .In control apparatus, a plurality of Wheatstonetbridge circuits, means tor varying the resistances of said circuits, said circuits and resistance varying means being so related that the deadpoints of the respective circuits are non-coincident, means for cutting out each of said circuits when a resistance-varying element thereof "approaches or reaches a deadspot of said circuit, and relay mechanism controlled by the balance circuits of said bridge circuits. 7

18. In control apparatus, a plurality of parallel .Wheatstone bridge circuits each'comprising resistances at a control station, resistances at a controlled station and a balance circuit connecting said sets of resistances, movable contacts at each of said stations in electrical connection with the respective resistances and balance circuits for varying the respective resistances at the two stations,

said circuits and resistance-varying means being sorelated that the dead-pointsfiof the respective circuits are non-coincident, and relay mechanism controlled by the balance circuits of said bridge circuits.

19. In control apparatus,;a plurality of parallel Wheatstone bridge circuits each comprising resistances at a control station, resistances at a controlled station and a balresistances, movable contacts at each of said stations in electrical connection with the respective resistances and balance circuits for varying the respective resistances at the two stations, said circuits and resistancesvarying means being so related that the dead-points of the respective circuits are non-coincident, means for cutting out each of said circuits as a resistance-varying means thereof reaches or approaches a dead-point therein, and relay mechanism controlled by the balance circuits of said bridge circuits.

20.. In control apparatus, Wheatstone bridge mechanism comprising a plurality of pairs of resistances at a control station, a plurality of contact bars at said station, movable contacts for connecting said pairs of resistances to'isaid'bars respectively, a plurality of pairsof resistances at a controlled station, a plurality of contact bars at said station, movable contacts for connecting said last-named pairs of resistances to said lastnamed bars respectively, a plurality of balancecircuits connecting respective bars at the two stations, means for cutting out each of said balance circuits as a contact in electrical connection therewith reaches or approaches a dead-point in the corresponding resistances, and relay mechanism controlled by said balance circuits. J

' 21. In control apparatus, Wheatstone bridge mechanism oomprising'a plurality of pairs of resistances at a control station, a plurality of contact bars at said station, movable circumferentially-spaced contacts for connecting said pairs of resistances to said bars respectively, a plurality of pairs of resistances at a controlled station, a plurality of contact bars at said station, movable circumfere ntially-spaced contacts for connecting said last-named pairs ,of resistances to said last-named bars respectively, a plurality of balance circuits connecting re spective bars at the two stations, means for cutting out each of said balance circuits as a contact in electrical connection therewith reaches or approaches a dead-point in the corresponding. resistances, and relay mechanism controlled by said balance circuits.

I 22. In control apparatus, Wheatstone bridge mechanism comprising a plurality of pairs of resistances at a control station, a

plurality of contact bars at said station,

movable contacts for connecting said pairs of resistances to said bars respectively, a plurality of pairs of resistances at a controlled station, a plurality of contact bars at said station, movable contacts for connecting said last-named pairs of resistances to said last-named bars respectively, a plurality of balance circuits connecting respective bars at the two stations, the contact bars at one of said stations being broken whereby each of said balance circuits is cut out as a contact in "electrical connection there- 40 with reaches or approaches a dead-point in the corresponding resistances, a motor for moving said last-named contacts, and relay mechanismcontrolled by said balance circuits for controlling the operation of said motor.

23. In control apparatus, Wheatstone bridge mechanism comprising a plurality of pairs of resistances at a control station, a plurality of contact bars at said station, movable eircumferentialy spaced contacts for connecting said pairs of resistances to said bars respectively, a plurality of pairs of resistances at a controlled station, a, plurality of contact bars at said-station, movances to said last-named bars respectively, a plurality of balance circuits connecting respective bars at the two stations, the contact bars at one of said stations being broken whereby each of said balance circuits is cut out as a contact in electrical connection therewith reaches or approaches a deadpoint in the corresponding resistances, a

able circumferentially-spaced contacts for 1' connecting said last-named pairs of resistmotor for moving said last-named contacts,

' and relay mechanismcontrolled by said balance circuits for controlling the operation of said motor.

24,-. In control apparatus, Wheatstone bridge mechanism comprising a plurality of pairs of resistances at a control station, a plurality of pairs of resistances at a controlled station, a plurality of concentric contact bars at each of said stations, a rotatable handle carrying a plurality of cireumferenpairs of resistances at a control station, a

plurality of pairs of resistances at a controlled station, a plurality of concentric con- 'tact bars at each of said stations, arotatable handle carrying a plurality of circumferentially-spaced contacts for connecting, the pairs of resistances at the control station to the respective contact bars, a rotatable index carrying a plurality of circumferentiallyspaced contacts for connecting the pairs of resinstances at the controlled station to the respective contact bars, a plurality of balance circuits connecting respective contact bars at the two stations,'means for predeterminately cutting out each of saidbalance circuits as a contact in electrical connection therewith reaches or aproaehes a dead-point in the corresponding resistances, a motor for rotating said index, and clay mechanism controlled by said balance circuits for controlling the operation of said motor.

26. In control apparatus, Wheatstone bridge mechanism comprising a plurality ofpairs of resistances at a control station, a plurality of pairs of rem'stances 'at a controlled station, a plurality of concentric contact bars at each of said stations, a rotatable handle carrying a plurality of circumferentially-spaced contacts for; connecting the pairs of resistances at the control station to the respective contact bars, a rotatable index carrying a plurality of circumferentiallyspaced contacts for connecting the pairs of resistances at the controlled station to the respective contactbars, a plurality of balance circuits connecting respective contact bars at the two stations, the contact barsat. 7 one of said stations belng broken whereby each balance circuit is cut out as a contact 4.

in electrical connection therewith reaches or approaches a dead-pointin the corresponding resistances,

emotor' for rotating said index, and relay mechanism controlled by 5 said balance 01 rcnits for controlling the opt eration of said motor.

- In testimony whereof 'I have signed this, 

